Provide 2 examples that prove Jack will hurt Piggy if Ralph quits as leaderAfter this quite unsuccessful meeting, Ralph begins to question whether...

This conversation follows the unsuccessful attempt to bring order once again to the fragile society, and establish a firmer sense of rules and guidelines. Jack and the hunters have essentially broken from the larger group, and will quickly rise as an opposing force to Ralph's try at some form of civilization.

Piggy has several reasons to fear Jack with the protection of Ralph. Even though Jack and Ralph are pitted at odds, they maintain a shaky truce, based upon, if not mutual respect, then mutual fear. Jack has no such regard for Piggy, however. From his first introduction, he has heckled and belittled Piggy's ideas, often refusing to let him speak, even when holding the conch shell. When Piggy does speak, he rouses the rest of the boys against his ideas and often drowns him out through his own shouts. While this is not physical abuse, it certainly paves the way through emotional/mental torture to a more direct attack.

Furthermore, Jack refuses Piggy meat after the first "successful" pig hunt in Chapter 4. His excuse is that Piggy did not hunt, and Piggy's protests that neither Simon nor Ralph took part go unheeded. Finally, Simon gives him a bit of meat, enraging Jack. Again, there is no actual physical violence, but there's certainly a threat of starvation and alienation from the larger group.

Finally, Jack does physically attack Piggy, also in Chapter 4. Although Jack has brought meat, they have also let the fire die, losing a chance at rescue. Piggy chastises Jack for this, and Jack responds by punching him the stomach. He then smacks Piggy on the head, sending his glasses flying and breaking one lens. This is the moment that reveals what Jack is capable of doing, and what lengths he will go to in order to achieve his purpose.

Thus, Piggy has plenty to fear from losing Ralph as leader. Jack already loathes him, and has demonstrated his feeling son many occasions. In addition, if Ralph steps down, Jack may still respect him too much to take action, but might instead take out his rage for the former leader on Piggy.